A problem which is often experienced with openings between environments which are required to be held at different temperatures, is the need to provide a closure in the form of a door for the opening, which door is operable to move between opened and closed positions and in particular, once opened, to return to a closed condition as quickly as possible so as to be able to maintain the temperature in the cooler environment and thereby allow the maintenance of the goods in the cooler environment at the required temperature.
The applicant, in their co-pending application GB2385659, disclose such a door system which incorporates a first wall or curtain which forms an external surface facing into one of the environments and a second, opposing, spaced, wall or curtain which forms the external surface facing into the second environment.
A further problem which is experienced is the creation of condensation on the door itself which can lead to, firstly, the gathering of water or liquid in the vicinity of the door and, if frost forms, the malfunction or poor operation of the door structure.
The applicant's co-pending application discloses the ability to pump air, which is required to have a relatively low humidity, through the cavity defined between the first and second walls of the door and said air, which may also be heated but need not necessarily be so, serves to reduce the tendency of moisture or frost being created on the door.